1. Field of the Invention
The present invention relates to a self-diagnostic circuit for an I/O circuit system incorporated in the controller of a semiconductor manufacturing apparatus or the like.
2. Description of the Related Art
In general, many driving systems and various sensors (to be referred to as driving portions) are attached to a semiconductor manufacturing apparatus or the like in order to drive each building portion. For example, to operate the driving systems, a main controller having a microcomputer properly acquires analog or digital sensor outputs from the sensors of the driving systems. The main controller analyzes these sensor outputs, and sends a control instruction to each driving system in accordance with a control sequence or control program in order to cause the driving system to perform a predetermined operation. For example, to introduce process gas into a processing chamber, the main controller instructs a flow controller of the gas species or gas flow rate corresponding to processing to be performed for a semiconductor wafer (to be referred to as a wafer hereinafter). The flow controller sends a return signal concerning the gas flow rate or the like to the main controller, and feedback control is executed. Similarly, the main controller instructs a high-frequency power supply for generating a plasma of a high-frequency power output value to be applied. A stable plasma is generated by control based on a return signal from the high-frequency power supply or a sensor signal from a sensor arranged in the processing chamber. The main controller drives an exhaust system on the basis of a measurement value from a pressure gauge which detects the internal pressure of the processing chamber. The main controller controls the pressure so as to set a desired pressure in the processing chamber.
Control signals and sensor signals exchanged between the main controller and each driving system or sensor system are used after conversion into analog and digital signals.
Each building portion which constitutes an apparatus generally undergoes part replacement, adjustment, and the like by general maintenance. Depending on the degree of maintenance, a signal cable which connects building portions may be disconnected. When the signal cable is disconnected, whether the cable is correctly connected must be checked at the start of operation.
Even with periodic maintenance, part replacement, adjustment, and the like, damage to a part, an adjustment error, short-circuiting in a circuit, or the like may occur for some reason. Quick corrective maintenance is required for such a fault. It is therefore important to quickly detect which of many circuit networks or which of parts suffers a fault.
In a conventional apparatus arrangement, a fault can be detected at each building portion within a relatively short time. However, when building portions are assembled into an apparatus and connected to each other by cables or the like, it is very difficult to detect which part suffers an electrical defect or which portion was the cause. For this reason, building portions must be checked by disconnecting cables, or a faulty portion is detected on the basis of empirical knowledge of the operator or by checking the previous fault log. A long time is taken for detecting a faulty portion.